FIELD OF THE INVENTION
The present invention relates to a hybrid integrated circuit apparatus in which a power element is mounted, and more particularly to a hybrid integrated circuit apparatus with a reduced switching noise of the power element and an improved dielectric strength of wiring part of the power element.
Two kinds of circuit substrates have been used in conventional power modules in which power elements were mounted in a hybrid integrated circuit. The first substrate was a circuit substrate in which an upper surface of a metal substrate made of Cu or Al as a main component was insulated with epoxy resin or polyimide resin, etc. to which inorganic fillers such as SiO2 were added. The second one was a circuit substrate in which an upper surface of a metal substrate was insulated with ceramics.
The former was mainly used for a product of 600 V/30 A or less capacity, and the latter was used for the product that exceeds 600 V/30 A capacity.
On the other hand, there is a power module using a combined circuit substrate of the above mentioned two kinds of substrates; i.e. a circuit substrate in which an upper surface of a metal substrate is insulated with an organic films such as epoxy resin on one part and with ceramics on another part.
The power module of this type is disclosed in Japanese patent laid-open print 3-195053. The power semiconductor element is connected to the metal substrate through ceramic chips such as aluminum nitride of which heat conduction is good. Cu is used as the metal substrate.
Small signal elements such as driver IC's are connected to the wirings formed on the insulation layer coated on metal substrate 1. Polyimide resin is used as the insulating layer.
In this power module, input and output wirings of the small signal circuit and the power semiconductor element are formed on the polyimide resin. Only the power semiconductor elements are connected to the metal substrate through the ceramic chip. And, the small signal circuit and the power semiconductor element are connected to each other with aluminum wire.
Thermal dissipation can be improved by using ceramics for mounting portion of the power semiconductor element in the above power module. However, with an increase in electric current of a power semiconductor device, a noise that is generated at the time of switching and a noise from the input/output wiring may enter into the wiring formed in the vicinity of the power element.
The noise entered in the wiring for the small signal generates operation errors of a driver IC or a microcomputer.
In the power module of this type, two kinds of insulators such as ceramics and polyimide, and a collector electrode and an input/output wiring of the power semiconductor element are connected with Al wire. When this structure is applied to high power semiconductor elements, there may be a problem of an increase in wiring resistance that leads to an increased in power loss of the semiconductor element. Because a copper plate is used as a metal substrate for the power hybrid integrated circuit, soldering is easy when the ceramic chip is connected to the substrate, and heat dissipation is also good.
But, there is a problem that the weight of whole system using this hybrid integrated circuit becomes heavier since copper is heavy.